Patent Grant
7768660
The present invention relates to the ellipsometric investigation of films beneath a top surface of a sample, and more particularly to the use of a focused electromagnetic beam which is caused to impinge on the top surface of a tube shaped sample, to investigate a film coating on its inner surface during fabrication thereof and/or thereafter.
Generally, a problem inherent in monitoring electromagnetic radiation which is reflected from a sample outer surface is that it often is contaminated with reflections from a backside thereof. One approach to preventing this problem is to roughen the backside. Another is to place a mask on the surface of the sample which allows surface reflections to proceed, but prevents backside reflections from exiting. Another approach yet is to place a blocking means between the sample and the detector which blocks backside reflections but lets front surface reflections proceed into the detector. Said approaches, however, do not allow for selectively monitoring electromagnetic radiation reflected from the front or backside. In that light it is noted that backside reflected electromagnetic energy contains information which is different from that contained in outer surface reflections.
Continuing, it is also disclosed that ellipsometry monitors the product of refractive index and thickness in samples investigated thereby, and that said parameters are correlated in what can be termed an optical thickness. A known approach to breaking the correlation is to obtain data from two samples comprising the same material(s) but which samples are of different thicknesses. Simultaneously regression of the data obtained from both sides onto corresponding mathematical models leads to substantially uncorrelated evaluation of refractive index and thicknesses.
It is also mentioned that it is known to obtain data from front and backsides of a sample and simultaneously regress said data onto a mathematical model therefore.
More on-point as regards the present invention, it is known to cause a polarized electromagnetic beam to impinge on the top surface of a sample along with monitoring reflected electromagnetic radiation therefrom to enable characterization of the sample as a composite. The detected reflected electromagnetic radiation generally includes interfering components which reflect from said top surface and from various interfaces between a plurality of layers.
It is also known to focus electromagnetic radiation onto a surface of a sample (e.g. 25 micron spot size), comprised of a front and back, and that electromagnetic radiation reflected from the front and back can become spatially separated from one another when such focusing is utilized. This avoids the complication of interference effects between various components reflected from different interface locations in the sample, by allowing separate monitoring of the various reflections. That is, the electromagnetic radiation reflected from a coating on the bottom of a sample can be monitored substantially free of components reflected from the top surface and various intervening interfaces.
further, it is known that appropriate orientation of an impinging beam of electromagnetic with respect to a curved sample surface can make the curved surface appear essentially as a flat surface, (e.g. align the beam orientation with a longitudinal dimension of a cylinder), to an electromagnetic beam of small diameter.
In addition, a Co-Pending patent application Ser. No. 11/288,785 it is disclosed to use a detector to selectively intercept portions of a focused beam caused to impinge on a sample comprising a top surface and at least one interface therebelow.
Known Patents and Published Applications are:
The various known factors recited above however, have not, to the Applicant's knowledge, been combined to provide a non-destructive method of characterizing a thin film coating present on the inner surface of a tube shaped sample. Need remains for a system and non-destructive method which allows investigation of a film present on an inner surface of a tube shaped sample.
When faced with characterizing, for instance, the optical constants and/or thickness of a thin film present on the inner surface of a tube shaped sample, an obvious approach is to obtain a broken piece thereof and use conventional ellipsometry methodology to directly apply a polarized electromagnetic beam to said thin film coating. A strong reflection from the surface of such a film can be analyzed conventionally with good results being achieved. This approach is fine where, say, broken pieces of the tube are available, but does not work in a setting where, for instance, the tube can not be broken in order to provide such direct access to the coating on said inner surface. This can, for instance, occur during manufacture fabrication of a tube which has a coating on the inner surface thereof and it is desired to monitor the fabrication results in real time.
The present invention, in a preferred mode of operation applies focused beam electromagnetic radiation to the top surface of a tube shaped sample, in combination with the detection of a component of said electromagnetic beam which is reflected from an interface between the inner surface of said tube and a thin coating thereon. Use of a focused beam applied at an oblique angle and preferably in a direction aligned along the longitudinal dimension of the tube shaped sample, (to best approximate incidence on a flat sample surface), results in separately detectable reflections from the top surface (i.e. the outer surface of said tube shaped system), and from the interface between the inner surface thereof and the film coating thereupon. Analysis of said separately detected reflected electromagnetic radiation from the interface between the inner surface thereof and the film coating thereupon allows determining optical constants and/or thickness of said film coating.
It is noted that the beam can be directed to approach the tube shaped sample in a direction coincident with its small lateral dimension, but this can cause the beam to impinge on a surface which does not best approximate a flat sample surface, thus directing the beam along the major dimension of the tube is preferred.
A present invention system is then sequentially comprised of:
Said system can further comprise providing at least one selection from the group consisting of:
A method of non-destructively investigating properties of a film coating present on an inner surface of a tube shaped system during fabrication thereof or thereafter, comprises the steps of:
practicing steps a and b simultaneously or in either order;
a) providing a tube shaped sample comprising outer and inner surfaces, said tube shaped sample having a film coating present on its inner surface;
b) providing a system for causing a focused beam of electromagnetic radiation to impinge upon the outer surface of said tube shaped system at an oblique angle of incidence, and a detector situated to receive a component thereof reflected from the interface between said inner surface of said tube shaped sample and said film coating present thereupon;
c) collecting and analyzing said electromagnetic radiation reflected from the interface between said inner surface of said tube shaped sample and said film coating present thereupon, to determine the optical constants and/or thickness of said film coating.
Another method of selectively monitoring reflections from a sample during fabrication thereof or thereafter, comprises the steps of:
a) providing a system which is sequentially comprised of:
b) causing a beam of electromagnetic radiation to reflect from said sample; and
c) moving at least one selection from the group consisting of:
A method of selectively monitoring outer surface or interface reflections from a sample, or transmission therethrough during fabrication thereof or thereafter, comprises the steps of:
a) providing a system which is sequentially comprised of:
b) causing a beam of electromagnetic radiation to at least partially reflect from said sample at an oblique angle; and
c) causing said detector to selectively monitor electromagnetic radiation reflected from the sample outer surface or from the interface between said tube shaped sample and the film coating on said inner surface or which is transmitted through said sample and obtaining data;
Another method of pursuing uncorrelated determination of refractive index and thickness of a film on an inner surface of a tube shaped sample during fabrication thereof or thereafter, comprises:
practicing steps a and a′ sequentially or simultaneously in either order:
a) providing a system which is sequentially comprised of:
a′) providing a mathematical model of said sample;
b) causing a beam of electromagnetic radiation to impinge onto said sample at an oblique angle of incidence; and
c) independently monitoring at least two selections form the group consisting of:
d) simultaneously regressing at least two monitored data sets obtained in step c onto said mathematical model provided in step a′.
Any of the foregoing methodology can involve analysis of the reflections from the outer surface and said interface between said tube shaped sample and the film coating on said inner surface thereof are analyzed separately with the reflection from the outer surface providing information about the surface region of the sample and the reflection from the interface between said tube shaped sample and the film coating on said inner surface thereof providing information about the film.
It is mentioned for emphasis that the foregoing methods preferably involve providing a focusing element in the oblique angle of incidence incident beam, and that said focusing element can comprise refractive or reflective components, or a combination of refractive and reflective components.
Any of the foregoing methods can further comprise performing at least one selection from the group consisting of:
In any of the foregoing Methods the step of providing a system further can involve providing at least one selection from the group consisting of:
Any of the recited methods can further comprises a selection from the group consisting of:
It is specifically noted that a present invention system can comprise any combination of movable or fixed location tube shaped sample and movable or fixed location detector. such as:
In addition, it is noted that the terminology “a focusing element positioned such that electromagnetic radiation from said source is directed at said sample at a plurality of an oblique angles”, means that a range of angles of incidence around the beam oblique angle of incidence is effected by the focusing element.
Finally, it is specifically noted that the present invention can be practiced during the fabrication thereof as the film on the inner surface of said tube shaped sample is deposited or otherwise applied, or during post fabrication investigation.
The present invention will be better understood by reference to the Detailed description Section of this Specification, in combination with the Drawings.
a demonstrates that a detector (DET) can comprise a plurality of detector elements (DE's) and be positioned stationary with respect to reflected beams.
b shows that a detector can be provided signal via a movable light fiber.
It is mentioned that while it is shown to move the Detector (DET) to selectively intercept various components of the Reflected Electromagnetic Beam, (e.g. the reflection from the Top Surface (TR) or the Interface (IR)), it is also possible to alternatively or in addition to, move the Sample (T) and/or Electromagnetic Beam (EM) upward or downward. See arrows (AR) in
It is also noted that continuous or step-wise rotation of the Tube Shaped Sample (T) as it is viewed in
Also, while a refractive Focusing Lens (FL) is shown in
Having hereby disclosed the subject matter of the present invention, it should be obvious that many modifications, substitutions, and variations of the present invention are possible in view of the teachings. It is therefore to be understood that the invention may be practiced other than as specifically described, and should be limited in its breadth and scope only by the Claims.
This Application directly Claims Benefit of Provisional Application Ser. No. 60/842,456 Filed Sep. 6, 2006. This Application is also a CIP of application Ser. No. 11/288,785 Filed Nov. 30, 2005 now U.S. Pat. No. 7,385,698 and therevia of Ser. No. 11/098,669 Filed Apr. 2, 2005 now U.S. Pat. No. 7,239,391 and therevia of Ser. No. 10/238,241 Filed Sep. 10, 2002 now U.S. Pat. No. 6,937,341 and therevia of Ser. No. 09/756,515 Filed Jan. 9, 2001, (now U.S. Pat. No. 6,455,853). Further this Application is a CIP of Ser. No. 10/194,881 Filed Jul. 15, 2002 now U.S. Pat. No. 6,940,595 and therevia of Ser. No. 09/916,836 Filed Jul. 27, 2001, (now U.S. Pat. No. 6,636,309). This Application also Claims Benefit of Provisional Application Ser. No. 60/639,097 Filed Dec. 27, 2004.
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| 7385698 | Welch et al. | Jun 2008 | B1 |
| 20020113200 | Hajjar et al. | Aug 2002 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 60842456 | Sep 2006 | US | |
| 60639097 | Dec 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11288785 | Nov 2005 | US |
| Child | 11897401 | US | |
| Parent | 11098669 | Apr 2005 | US |
| Child | 11288785 | US | |
| Parent | 10238241 | Sep 2002 | US |
| Child | 11098669 | US | |
| Parent | 10194881 | Jul 2002 | US |
| Child | 10238241 | US | |
| Parent | 09916836 | Jul 2001 | US |
| Child | 10194881 | US | |
| Parent | 09756515 | Jan 2001 | US |
| Child | 09916836 | US |
